He won the 2004 Tony Award for Best Book of a musical for Avenue Q, written with composers Robert Lopez and Jeff Marx, which opened on Broadway in 2003, and continued to a West End run and two national tours as well as dozens of international productions. After six years on Broadway the show moved Off-Broadway, where its run continues. His plays include The Further Adventures of Hedda Gabler which was commissioned by and received its world premiere at South Coast Repertory in January, 2006; The Plank Project (a parody of documentary theater pieces like The Laramie Project); the multi-play cycle Balls; The Hiding Place, a romantic Manhattan comedy which received its New York debut at the Atlantic Theater Company; and the dark comedy Suicide Weather.